Such methods deform the cross-section of the long metal member in the heating zone. This causes a portion of the periphery of the metal member to be moved away from the collar, while another portion of the periphery moves towards it. The first portion is therefore not heated to as high a temperature as the second, which can cause geometrical and metallurgical defects.
The present invention aims to remedy this drawback and to provide a method and apparatus for bending a long metal member which method and apparatus avoid such defects.